A unifying pathological feature of cystic fibrosis (CF) is the obstruction of the respiratory, gastrointestional, and reproductive tracts by mucus secretions. These secretions consist of extremely large heterogeneous glycoproteins known as mucins. Mucins are over-synthesized in CF, their terminal glycosylation patterns are altered, and they have an increased affinity for Pseudomonas aeruginosa, an organism which colonizes in the lungs of CF patients and is the primary cause of death. As a result of former studies, CF has been characterized as "generalized" mucus obstruction. These studies relied upon reagents directed to carbohydrate structures which are present on more than one mucin core protein, and therefore, results have been vague. Due to development of antibodies to the core proteins of mucins and to the cloning of these mucin genes, we now have the tools necessary to determine which specific mucins are involved in CF. Using as a model for the disease, a CF "knockout" mouse and mice transgenic for a mutated human CFTR (AF508) gene, we propose to study mucin expression at a molecular level. We currently have antibodies to three of the five known rodent mucins (Muc- 1, Muc-2 and rMuc176) with antibodies to Muc-4 in preparation. These antibodies, and any others which may become available, will be used to study tissue and developmental expression of the mucin glycoproteins in the CF mice as compared to wild-type controls. We also have DNA probes for Muc-1, Muc-2, Muc-t, rMuc176, and ASGP-2 which will be used in northern analysis of CF tissue to observe tissue-specific expression and expression levels of mucin genes. To further study tissue expression levels we will use the sensitive technique of RT-PCR. Identification of the mucin gene(s) responsible for increased mucin production will enable us to examine the regulatory sequences and to identify regulatory factors in mucin synthesis. Ultimately, it may be possible to therapeutically interfere with the mucin production that is one of the major secondary complications of CF.